The relationship between the failure of energy and the disturbances in monoamine metabolites was investigated in the brain of Mongolian gerbils subjected to bilateral ischemia only (5 or 15 min) or with 1 hour reflow. The use of microwave irradiation to fix the brain allowed the measurement of labile metabolites and neurotransmitters from the same sample of tissue. Both the energy charge and the content of ATP and P-creatine were reduced to the same extent in the hippocampus and striatum at 5 min and 15 min of blood supply-deprivation to the brain while the changes in monoamines were only found after 15 min of ischemia. On the other hand, in reflow the energy charge and the immediate source of energy recovered almost completely in these structures whereas the changes in the content of the monoamines were not only present but the level of NE was also reduced in recirculation after 5 min ischemia. These results clearly demonstrate that the changes in the tissue energy charge are not directly associated with the disturbances of cerebral amines in ischemia.